Field of the Invention
This invention relates to an improved method for selectively synthesizing pyridine and 3-alkylpyridine, e.g., 3-picoline, by reaction of ammonia and a carbonyl compound selected from the group consisting of formaldehyde, aldehydes containing from 2 to 4 carbon atoms, and ketones containing from 3 to 5 carbon atoms in the presence of catalyst comprising a synthetic porous crystalline material. The improvement of the present invention involves increased yield and pyridine and 3-alkylpyridine, e.g., 3-picoline, product, and is realized by the required use as catalyst of a composition comprising a specific synthetic porous crystalline material, such as, for example, MCM-49, or one characterized by an X-ray diffraction pattern including interplanar d-spacings at 12.36.+-.0.4, 11.03.+-.0.2, 8.83.+-.0.14, 6.18.+-.0.12, 6.00.+-.0.10, 4.06.+-.0.07, 3.91.+-.0.07, and 3.42.+-.0.06 Angstroms, e.g., MCM-22.
Another aspect of this invention involves manufacture of 3-pyridinecarboxylic acid, i.e., nicotinic acid, by reaction of 3-picoline recovered from the product of the above reaction with an oxidative reagent, such as, for example, KMnO.sub.4.
Description of Prior Art
Reaction of acetaldehyde or certain other low molecular weight aldehydes and ammonia either in the absence or presence of methanol and/or formaldehyde to yield pyridine and alkyl derivatives thereof has been carried out in the presence of amorphous silica-alumina composites containing various promoters. See, for example, U.S. Pat. Nos. 2,807,618 and 3,946,020. The yields of desired products using the latter catalysts have been poor. Alkylpyridines have also been synthesized, as reported in Advances in Catalysis, 18, 344 (1968), by passing gaseous acetaldehyde and ammonia over the crystalline aluminosilicates NaX and H-mordenite. While initial conversion utilizing these materials as catalysts was high, catalyst deactivation by coking was rapid, providing a commercially unattractive system, characterized by poor catalytic stability.
The next step in the progression of pyridine and alkylpyridine synthesis was the discovery that the synthetic crystalline zeolites having an intermediate pore size as measured by the Constraint Index of the zeolite being between 1 and 12, e.g., ZSM-5, provided commercially useful yields and product selectivities. U.S. Pat. No. 4,220,783 was pioneer in this discovery, teaching synthesis of pyridine and alkylpyridines by reacting ammonia and a carbonyl reactant which is an aldehyde containing 2 to 4 carbon atoms, a ketone containing 3 to 5 carbon atoms or mixtures of said aldehydes and/or ketones under effective conditions in the presence of a catalyst comprising a crystalline aluminosilicate zeolite having been ion exchanged with cadmium and having a silica to alumina ratio of at least about 12 and a Constraint Index within the approximate range of 1 to 12.
Use of the same crystalline material catalyst component as in U.S. Pat. No. 4,220,783, i.e., having a Constraint Index of from 1 to 12, e.g., ZSM-5, in a fluidized or otherwise movable bed reactor is taught in U.S. Pat. No. 4,675,410. U.S. Pat. No. 4,866,179 teaches synthesis of pyridine by reaction of ammonia and a carbonyl compound, preferably with added hydrogen, over catalyst comprising a crystalline aluminosilicate zeolite which has been ion exchanged with a Group VIII metal of the Periodic Table. The crystalline aluminosilicate zeolite has a silica to alumina mole rate of at least 15, preferably 30 to 200, a Constraint Index of from 4 to 12, e.g., ZSM-5, and the process provides a high and selective yield of pyridine.
U.S. Pat. No. 5,013,843 teaches addition of a third aldehyde or ketone to a binary mixture of aldehydes and/or ketones used in preparing mixtures of pyridine and alkyl-substituted pyridines in large scale continuous processes. In a preferred system, propionaldehyde is added to a binary mixture of acetaldehyde and formaldehyde to produce beta-pyridine and pyridine. The catalyst for this process is a crystalline aluminosilicate zeolite in the acidic form having a Constraint Index of from 1 to 12, e.g., ZSM-5.
Applicants know of no prior art teaching the present improvement in selective synthesis of pyridine and 3-alkylpyridine, especially 3-picoline, over catalyst comprising crystals of the presently required zeolite.